Seats for vehicle having various adjustment functions may be generally classified into those having recliners, tilters and lifters for adjusting the posture of the seated person and those having thigh supports, side supports and lumber supports for adjusting the feeling and/or the body pressure distribution of the seated person. They are further classified into those which are manually adjusted and those adjusted by external force.
Specifically, this invention relates to a seat for vehicle which can adjust the feeling and the body pressure distribution of the seated person by external force and which can prevent the excessive increase in the air pressure due to temperature rise in the passenger compartment after the passenger has gotten off the vehicle.
Conventionally, such a seat for vehicle is typically provided with a power element, consisting, for example, of a motor and gears, for each adjustable portion of the seat and is controlled by mechanical adjustment mechanism, causing it to be heavy and complex and is therefore costly. It has been proposed to use air pressure as power means but such a system necessarily requires a pressure regulating valve for reducing the high air pressure of a pressure source to a level suitable for use and, since a pressure regulating valve requires a high level of precision for its manufacture and maintenance, tends to be costly and unreliable. Furthermore, as the number of the portions in the seat to be adjusted increases, the structure tends to be complex and the adjustment becomes increasingly cumbersome while the cost of manufacture becomes prohibitively high.
For instance, in Japanese patent application No. 59-9773 and Japanese Utility Model application No. 59-7311, the same applicant proposed pneumatically controlled seats for vehicle according to which the air pressures of the air bags are conveniently controlled by certain air control means. According to these pneumatically controlled seats, because the adjustment of the air pressure of each of the air bags may be quickly and readily accomplished, the comfort and the impression of the vehicle may be substantially improved by varying the body pressure distribution and the feeling of the seated person as desired. However, since they require either a plurality of pressure regulating valves or a variable pressure regulating valve, they tend to be expensive.
Furthermore, when air bags are used for achieving a desired contour of the seat or a desired body pressure distribution, the air bags must be protected from excessive inflation which may be caused by an excessive temperature rise in the passenger compartment as is often the case in a car which is parked for a long time in hot weather or by malfunction of a pressure control unit.
In view of such shortcomings of the prior art, a primary object of this invention is to provide a seat for vehicle according to which a plurality of air bags embedded in the seat may be filled with air of desired pressure without without requiring a pressure regulator valve.
Another object of this invention is to provide an improved pneumatically controlled seat for vehicle according to which the efforts involved in setting up the pressures of air bags embedded in the seat are substantially eliminated through automatization of the setting up of the air pressures of the air bags.
Yet another object of this invention is to provide an improved pneumatically controlled seat for vehicle according to which the body pressure distribution may be automatically and individually adjusted for each individual person.
Yet another object of this invention is to provide an improved pneumatically controlled seat for vehicle according to which the body pressure distribution of the seated person may be variably and automatically controlled according to the operating conditions of the vehicle so that the optimum body pressure distribution may be attained at all time.
Yet another object of this invention is to provide an improved pneumatically controlled seat for vehicle which is free from the problems of excessive inflation of the air bags.